Hold down only the up & down arrow buttons (below the mode button) of the trip computer.
Turn the ignition to ON
After about 3 seconds the service reading will appear
Release the up & down arrows
You'll hear a beep
Hold the up & down arrows again & it should reset
Turn the ignition off.
No more service warning
(that's off memory so hope it's accurate- but it is in the standard manual that comes with the car).
The glove box manual states that you have to take your car to holden